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Alsema Sagitta 1:4 scale

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Alsema Sagitta 1:4 scale

Post by B Sharp »

As I mentioned in the “Who’s building what 22” thread a short while ago my project for this winter is the Alsema Sagitta.
Having drawn new wing plans and made adjustments to the Vic Steel fuselage and tailplane plans I was ready to make a start. I have spent a couple of weeks of spare moments cutting out formers and wing ribs. The formers are from Vic’s hand drawn plans and will likely require a bit of fettling to get a good fit. The wing I have planned is using HQ3.5/14 at the root and HQ3.5/10 at the tip. As the wing is highly tapered this should prevent tips stalls on landing approach.
Brian. :)
Attachments
3 View
3 View
The prototype
The prototype
000c.jpg
001.JPG
002.JPG
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Max Wright
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Location: Clayton Bay South Australia

Re: Alsema Sagitta 1:4 scale

Post by Max Wright »

She looks very sleek. 8-)

What is the story with the "tip tanks" ?

If I don't ask, I won't learn nuffin. ;)
Max
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Peter Balcombe
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Re: Alsema Sagitta 1:4 scale

Post by Peter Balcombe »

Max, i would have thought the tip “tanks” are more likely a combination of wing fence & tip skid - they are a bit like the plate types fitted to the 1950s Jaskolka i am currently building.
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Max Wright
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Location: Clayton Bay South Australia

Re: Alsema Sagitta 1:4 scale

Post by Max Wright »

Thanks, Peter.
Max
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B Sharp
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Re: Alsema Sagitta 1:4 scale

Post by B Sharp »

Max.
The data that I have collected on the Sagitta shows a number of options for the wingtips. The American examples (N6446 and N99999) both have flat plate wingtips as do PH-308, PH-319 and PH-403. I can find only one example with a round profile (like a jet wing tank) but I can’t make out the registration. The example I am modelling (PH-266) has the same elevation profile as the others but appears to have a thicker plan profile.
I think that their prime purpose is to form a wingtip skid. I don’t know if there is any aerodynamic benefit such as tip vortex management.
Brian. :)
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Max Wright
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Re: Alsema Sagitta 1:4 scale

Post by Max Wright »

It's all interesting, Brian. 8-)
Max
Jilles
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Re: Alsema Sagitta 1:4 scale

Post by Jilles »

Some more info on the Sagitta. There were 21 built including one Super Sagitta, this last one had a 17m wing span instead of 15m. I did wittness the maiden flight of this Super Sagitta myself. They were built at the Teuge Airfield in the Netherlands. It was a small workshop owned by Mr Bauling.
They did build many Grunau Baby"s after WW2 and these were called Bauling Baby's as did Fokker and were called Fokker Baby's
To keep the factory going the Sagitta was built, designed by Piet Alsama. It was suppose to compete with the Schleicher ka6 and Slingsby Skylarcs.
With the introduction of the first glass gliders of that time it never reached high production numbers.
I did fly the Sagita myself. It was a high performance glider for the time and required your constant attention to make it fly to max performance.
With the all around canopy the pilot had a 360 degree view. It could tip stall and some have come to grieve during landing by making the last low turn to slow. It did thermal well. The maximum speed was 270k/h, and the glide ratio 34:1 what for the time was very good. It was fully aerobatic, without any restriction apart from the max. speed
The tip tanks as far as I know were only used on the prototype. The production versions had the plank type tips ends because it reduced construction time/costs. The purpose was to protect the wing underside on the ground and also to reduce the tip stall a bit as was recognised during the first test flights.

I did design a 4.8m wing span model of the 15m Sagitta version. it was built in New Zealand and I did own and fly it myself untill it was sold to an other guy in N.Z. The model perfomed very well. I live in Australia so I had not much oppertunity to fly the Sagitta in N.Z. the reason it was sold in N.Z.
Cliff Evans has the details in case somebody is interested to build this model. The model 3 view drawing is attached
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3VIEW-A3.pdf
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Cliff Evans
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Re: Alsema Sagitta 1:4 scale

Post by Cliff Evans »

Jilles's plans are in the repository.
https://lasercutsailplanes.co.uk
https://patteaklegliders.co.uk
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B Sharp
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Location: Perthshire

Re: Alsema Sagitta 1:4 scale

Post by B Sharp »

Thanks for the additional info Jilles.
I did download your PDFs when they were first produced and it was my intension to build from your plans. However my date of birth has caught up with me and I am trying to restrict my builds to under 7kg as I have a long walk to carry the finished model up to my local slope. This is why I am building a 1:4 version.
However I have used your plans as a reference for the wings, tail and parts of the fuselage when planning my build. Thank you for that.
Brian.
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B Sharp
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Location: Perthshire

Re: Alsema Sagitta 1:4 scale

Post by B Sharp »

Sorry about the delay since my last post but I was a bit busy with other things and then we had the festive nonsense which took me on an expedition up to the wild and wintery north.

I have mounted the formers on my jig using ply up-stands to get them all sitting at the correct height. The top longeron and front upper support were dry-slotted into place and then the middle side longerons offered up to the formers. Of the thirteen formers seven had to be removed from the jig and the slots in the sides adjusted before the longerons looked anything like straight. I now have the partially complete structure dry jointed and clamped together while I investigate the positioning of the other longerons. What I have discovered is that several of the formers have slots for longerons where nothing appears on the plan or side elevation. Stranger and stranger? :shock:

To make things worse I have under ordered the ¼ square spruce that I require as I think I only calculated for one side of the fuselage. :x

Brian. :(
Attachments
Fuselage dry fitted to the jig.
Fuselage dry fitted to the jig.
005.JPG
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